Is it okay to freeze dry yeast at around -20 °C?

After adding a sachet of 71B yeast to a 50ml starter at about 40 °C, I've noticed absolutely no activity. The yeast sunk to the bottom of the container and just stayed there. This is the first time I experience this problem (at least I think it's a problem). Usually, the there will be a layer of froth and some minor bubbling in the container.

The only difference between this time and the 14 or so times I've done this before is that the yeast were frozen rather than refrigerated. According to a page at Lalvin's website, freezing their yeast for storage is acceptable.

I've already tried 3 sachets of frozen yeast and got the same odd result. I've just inoculated the last starter mixture because I thought I'm just being too paranoid. I hope I am, and I hope I'll see a thin layer of foam on top of my must in the next few days.

Topic starter wine yeast homebrew

Category Mac

1
answered at

Turns out that, at least in my case, freezing the dry yeast is actually a bad idea.

I made an experiment last night and I put two sachets of ICV D-47 in the freezer and two sachets in the fridge. This morning I took both of them out and let them warm up in the room.

I used the same activating mixture I've always used (some must + some nutrients) and split it into 4x 50ml portions. I pitched the yeast into the four bowls and waited 10-15 minutes.

Indeed, the two frozen yeasts sunk to the bottom and appeared completely dormant, while the ones kept in the fridge were active and had already formed a frothy layer.

Update: Apparently, the effect of freezing is almost diminished after I kept the yeast in room temperature for a couple of days.

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